1. Field of the Invention
The present invention relates to the downhole tools for use in subterranean formation evaluation and, more specifically, to the modularity of components in a downhole tool for use in a while-drilling environment.
2. Background of the Related Art
Wellbores (also known as boreholes) are drilled for hydrocarbon prospecting and production. It is often desirable to perform various evaluations of the formations penetrated by a wellbore during drilling operations, such as during periods when actual drilling has temporarily stopped. In some cases, the drill string may be provided with one or more drilling tools to test and/or sample the surrounding formation. In other cases, the drill string may be removed from the wellbore, in a sequence called a “trip,” and a wireline tool may be deployed into the wellbore to test and/or sample the formation. The samples or tests performed by such downhole tools may be used, for example, to locate valuable hydrocarbon-producing formations and manage the production of hydrocarbons therefrom.
Such drilling tools and wireline tools, as well as other wellbore tools conveyed on coiled tubing, drill pipe, casing or other conveyers, are also referred to herein simply as “downhole tools.” Such downhole tools may themselves include a plurality of integrated modules, each for performing a separate function, and a downhole tool may be employed alone or in combination with other downhole tools in a downhole tool string.
More particularly, formation evaluation often requires that fluid from the formation be drawn into a downhole tool (or module thereof) for testing in situ and/or sampling. Various devices, such as probes and/or packers, are extended from the downhole tool to isolate a region of the wellbore wall, and thereby establish fluid communication with the formation surrounding the wellbore. Fluid may then be drawn into the downhole tool using the probe and/or packer.
The collection of such formation fluid samples while drilling is ideally performed with an integrated sampling/pressure tool that contains several modules each for performing various functions such as electrical power supply, hydraulic power supply, fluid sampling (e.g., probe or dual packer), fluid analysis, and sample collection (e.g., tanks). Such modules are depicted, for example, in U.S. Pat. Nos. 4,860,581 and 4,936,139. Accordingly, a downhole fluid, such as formation fluid, is typically drawn into the downhole tool for testing and/or sampling. This and other types of downhole fluid (other than drilling mud pumped through a drill string) are referred to hereinafter as “auxiliary fluid.” This auxiliary fluid may be a sampled formation fluid, or specialty fluids (e.g., workover fluids) for injection into a subsurface formation. The auxiliary fluid typically has utility in a downhole operation, other than merely lubricating a drill bit and/or carrying away bit cuttings to the surface. This auxiliary fluid may be transferred between modules of an integrated tool such a sampling tool, and/or between tools interconnected in a tool string. Moreover, electrical power and/or electronic signals (e.g., for data transmission) may also be transferred between modules of such tools. A challenge is therefore to maintain a workable tool length (e.g. 30 feet) while performing the necessary fluid and electrical transfers between modules of the tool.
It will be further appreciated that several other applications will require the communication of fluid and electrical signals between sequentially-positioned modules or tools of downhole tool strings—in both wireline and “while drilling” operations. The “while drilling” operations are typically characterized as part of the measurement-while-drilling (MWD) and/or logging-while-drilling (LWD) operations, in which the communication of electricity (both power and signals) across connected tools or integrated tool modules is required. Various devices have been developed to conduct such while drilling operations, such as the devices disclosed in U.S. Pat. No. 5,242,020, issued to Cobern; U.S. Pat. No. 5,803,186, issued to Berger et al.; U.S. Pat. No. 6,026,915, issued to Smith et al.; U.S. Pat. No. 6,047,239, issued to Berger et al.; U.S. Pat. No. 6,157,893, issued to Berger et al.; U.S. Pat. No. 6,179,066, issued to Nasr et al.; and U.S. Pat. No. 6,230,557, issued to Ciglenec et al. These patents disclose various downhole tools and methods for collecting data, and in some cases fluid samples, from a subsurface formation.
Despite advances in sampling and testing capabilities in downhole tools, existing systems—particularly “while drilling” systems—are often limited to solutions for transferring electrical signals across tools or tool modules. Particular solutions include the various ring-type connectors at the joints of connected tubular members, such as “wired drill pipe” (WDP), as described in U.S. Pat. No. 6,641,434 assigned to Schlumberger, among others. Such WDP connectors are not known to provide for the transfer of electrical signals between the connected tubular members.
Connectors have also been provided for passing fluid through downhole wireline tools. Examples of such connectors are shown in U.S. Pat. No. 5,577,925, assigned to Halliburton and U.S. patent application Ser. No. 10/721,026. However, no known connectors are disclosed for connecting auxiliary flowlines that extend through and terminate at or near opposing ends of connected wellbore tubulars, or for facilitating a connection between connected components. Moreover, known connectors or connector systems have not been faced with the additional challenges of drilling tools which involve drill collar, drilling mud, space limitation and harsh drilling issues.
A need therefore exists for a connector that is adapted for communicating auxiliary fluid and/or electrical signals between tool modules and/or tools in a downhole tool string. It is desirable that such a connector exhibit the function of length adjustment so as to compensate for variations in the separation distance between the modules/tools to be connected. It is further desirable that such a connector exhibits the function of automatically sealing off auxiliary fluid flow therethrough upon disconnection of the connected modules/tools. It is further desirable that components connectable with the connector be modular, and be adaptable for use in varying environments and conditions.